There are many types of film deposition processes commonly used in the semiconductor fabrication field. One example process is referred to as a plasma-enhanced chemical vapor deposition (PECVD), which is a type of plasma deposition that is used to deposit thin films from a gas state (i.e., vapor) to a solid state on a substrate such as a wafer. PECVD systems convert a liquid precursor into a vapor precursor, which is delivered to a chamber. PECVD systems may include a vaporizer that vaporizes the liquid precursor in a controlled manner to generate the vapor precursor.
Another example film deposition process is referred to as atomic layer deposition (ALD), which also utilizes plasma energy to facilitate the deposition. ALD systems are used to produce very thin films that are highly conformal, smooth, and possess excellent physical properties. ALD uses volatile gases, solids, or vapors that are sequentially introduced (or pulsed) over a heated substrate. A first precursor is introduced as a gas, which is absorbed (or adsorbed) into the substrate and the reactor chamber is cleared of the gaseous precursor. A second precursor is introduced as a gas, which reacts with the absorbed precursor to form a monolayer of the desired material. By regulating this sequence, the films produced by ALD are deposited a monolayer at a time by repeatedly switching the sequential flow of two or more reactive gases over the substrate.
Chambers used to process PECVD and ALD processes require highly engineered structural construction so that the resulting films deposited on substrates are as uniform as possible and processes are repeatable from wafer-to-wafer. In such chambers, radio frequency (RF) power is supplied to enable excitation of gases in the form of a plasma, which leads to the deposition of a material film. The delivery of RF power is typically applied to either the substrate support (i.e., the pedestal) or the showerhead. In either configuration, RF power applied to the chamber needs to have an RF return to ground. Commonly, the chamber walls are grounded and RF power turns to ground via one or more conductive paths.
This process has worked well for some time, but as the demand continues to push for the manufacture of smaller feature sizes, more stringent demands are continually made upon chamber construction and engineered geometries. For example, some chamber designs usable for PECVD as well as ALD include multi-station designs. Multi-station designs are those that enable deposition processes to occur in multiple stations at the same time.
Such multi-station designs have added complexities associated with a spindle used to transfer wafers among the stations. The spindle is typically located in a center location, which places it adjacent to one side of a specific station. Unfortunately, for some processes, azimuthal non-uniformities in films deposited over the substrate may be introduced as influenced by the adjacent spindle.
It is in this context that inventions arise.